Exclusive paper products are often given a luxury appearance through printing. The print promotes the product and creates an image of the product to the customer.
However, printing is done as a separate process which is expensive. Further, printing inks can never be used on products which are in direct contact with food, or liquids, as the ink might migrate into the food or liquid product. Also, in hygienic products a direct contact from the printing to the skin needs to prevented, for instance are hygienic products like wet wipes, dressings and pads, never printed with printing inks etc. One such product is shown in SE537517C2 where a wet laid web, or a so called wet or moist tissue, comprising microfibrillated cellulose, is produced. That type of product would for instance not be printable, as is still substantially wet, or moist, when it is packaged and delivered to customers, i.e. it is not dried enough to be printable with ink, and as it is in some applications meant to be used as a hygienic wet wipe, a printing ink could cause skin irritations etc. Another example of such a product and process for producing the product is described in WO2015004324A1, where a water soluble biobased film is produced. Another method of providing paper products with a print, or an imprint is to punch holes or make an imprint into the material. Even though this type of process can be made in a conventional paper making machine, it is not always suitable. The holes or imprints may for instance cause the product to be prone to ripping etc., which is not desirable in a high speed production process.
There is thus a need for a process in which products can be provided with a print, without using printing inks or other types of colorants, for instance for identification and differentiation of the product before the customer or end user. Further there is a need for a printing process which can be fully incorporated into a wet laid process, or into a conventional paper or paperboard making process.